Thomas Jefferson Papers
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Thomas Jefferson to Benjamin Henry Latrobe, 27 August 1816

To Benjamin Henry Latrobe

Monticello Aug. 27. 16.

Dear Sir

As you were so kind as to give me your invention1 of the handsome and peculiarly American capital, I must give you mine of the new Dial to which that Capital has led. I had placed the Capital on a pedestal of the size proper to it’s diameter, and had reconciled their confluence into one another by interposing plinths successively diminishing. it looked bald for want of something to crown it. I therefore surmounted it with a globe and it’s neck, as is usual on gate posts. I was not yet satisfied; because it presented no idea of utility. it occurred then that this globe might be made to perform the functions of a dial. I ascertained on it2 two poles, delineated it’s equator and tropics, described meridians at every 15° from tropic to tropic, and shorter portions of meridian intermediately for the half hours quarter hours, and every 5. minutes. I then mounted it on it’s neck, with it’s axis parallel to that of the earth by a hole bored in the Nadir of our latitude, affixed a meridian of sheet iron, moveable on it’s poles, and with it’s plane in that of a great circle, of course presenting it’s upper edge to the meridian of the heavens corresponding with that on the globe to which it’s lower edge pointed. I then meridianised the globe truly, and presenting the outer edge of it’s moveable meridian to the sun, the shade of it’s thin plane, as a thread, designates on the hour lines of the globe, the meridian of the heavens on which he then is.

My globe is of locust, 10½ I. diameter, equal to the collar of the capital, & enables me to judge within one or two minutes of the solar time. this device may be usefully applied to the ornamental balls on gate-posts; or mounted on a balluster, or the frustum of a column, for the purpose of an ordinary dial. it is easily made by a common turner, with materials which every one possesses, and requires no calculation of hourlines, being adapted to every latitude by only fixing it on the point corresponding with the Nadir of the place.—perhaps indeed this may be no novelty. it is one however to me, and I offer it to you as an architectural embellishment which you may sometimes perhaps find occasion to use in your profession, and as a testimony of my readiness to embrace every occasion of renewing to you the assurances of my constant esteem & respect.

Th: Jefferson

PoC (DLC); at foot of text: “B. H. Latrobe esq.” Dft (DLC); incomplete; with PoC of TJ to Mathew Carey, 1 Sept. 1816, on verso. PoC of incomplete Dft (MHi); with PoC of TJ to Charles K. Mallory, 1 Sept. 1816, on verso.

For the peculiarly american maize capital sent by Latrobe, see Latrobe to TJ, 28 Aug. 1809. A photograph of the new dial as it was reconstructed at Monticello in 2001 is reproduced elsewhere in this volume.

1Dft ends here, with the following variant of the drawing of the sundial, on a pedestal but lacking the capital, in lower left-hand corner.

2Preceding two words interlined.

Index Entries

  • Capitol, U.S.; corncob capitals for search
  • corn; cob capitals search
  • Latrobe, Benjamin Henry; and capitals (architectural) search
  • Latrobe, Benjamin Henry; and TJ’s sundial search
  • Latrobe, Benjamin Henry; letters to search
  • Monticello (TJ’s estate); sundial at search
  • scientific instruments; sundials search
  • sundials; and corncob capital base search
  • sundials; at Monticello search